1. Field of the Invention
This invention relates to impact crushers which have a rotor carrying impellers arranged to strike and throw rock to disintegrate upon impact with target members spaced from the rotor, and in particular to an improved arrangement for attaching impellers to the rotor.
2. Description of the Prior Art
It has long been known to provide the rotor of impact crushers with easily replaceable impellers, by inserting the impellers endwise into axially extending peripheral slots which in end view appear as a dovetail (or partial dovetail), and with centrifugal force acting to wedge the impellers into seating engagement with slot walls. An example of such a crusher is the machine shown in a patent assigned to Allis-Chalmers Manufacturing Company, U.S. Pat. No. 1,331,969 of Feb. 24, 1920. However, as explained in U.S. Pat. No. 2,310,758 of Feb. 9, 1943, it was considered desirable to hold such impellers against very large centrifugal forces, by clamping arrangements acting with dovetail slots and having bolts in a plane perpendicular to the rotor axis. Other U.S. Pat. Nos. disclosing such arrangements include 2,747,803 of May 29, 1956; 2,767,928 of Oct. 23, 1956; 2,862,669 of 1958; and 3,151,816 of 1964.
Another clamping arrangement for holding impellers in dovetail slots involves members having wedging surfaces and movable by bolts parallel to the rotor axis. There are many U.S. Pat. Nos. showing such arrangements, including 2,192,606 and 2,223,584 of 1940; 2,258,075 of 1941; 2,325,605 of 1943; 2,373,691 and 2,378,475 of 1945; 2,486,421 of 1949; 2,585,943 and 2,588,434 of 1952; 2,646,224 of 1953; 3,096,035 of 1963; 3,146,961 of 1964; 3,202,368 of 1965; 3,295,773 of 1967; 3,455,517 of 1969 and 3,874,603 of 1975.
As will appear from the description of the present invention to follow, the object of the present invention is to provide a new and improved arrangement of the last-mentioned type. Of the prior patents referred to, it is believed that the most pertinent to the present invention are U.S. Pat. No. 2,258,075 and U.S. Pat. No. 3,874,603. U.S. Pat. No. 2,258,075 shows several arrangements including one in which a pair of conical members are drawn toward each other along an axis parallel to the rotor axis to lock hammers with rotor slots. U.S. Pat. No. 3,874,603, discloses a two-piece bushing fitted within the cylindrical cavity at each end of a rotor, and each of the bushings comprises a pair of bushing halves each having a convex semi-cylindrical outer surface. The bushing halves are arranged within the cylindrical cavity with one convex surface engaging the impeller defined portion of the cavity and the other convex surface engaging the slot wall defined portion of the cavity, and with a diametrical plane along which the bushing is split into halves being substantially parallel to the adjacent leading impeller face. The halves of each bushing defined therebetween an internal conical shaped cavity with an apex end pointed inwardly of the adjacent end of the rotor. A frusto conical plug is inserted into each bushing with apex ends pointed inwardly of adjacent ends of the rotor. A rod passes through central bores in both plugs, and nuts threaded on both rod ends hold the plugs relative to each other.